Conventionally, a system for integrally controlling the whole of a plurality of functional elements forming functions of a vehicle is proposed. This integrated control system in which the functional elements of a vehicle are divided in accordance with the functions is provided with a manager for management among the respective divided functions, as disclosed in U.S. Pat. No. 6,292,741 B1 (JP-A-2000-71819).
The manager is realized, for example, as a special ECU manager (electronic control unit) for managing control in an engine ECU and AT ECU as control functions of the engine and AT (automatic transmission), which are functional elements, to manage a vehicle axle torque of the whole of the vehicle as disclosed in US 2001/0056318 A1 (JP-A-2002-81345).
In this example, the engine ECU and the AT ECU transmit characteristic information of the engine and the AT to the manager ECU. The manager ECU transmits commands necessary for making the vehicle axle torque equal to a target value on the basis of the received characteristic information to the engine ECU and the AT ECU. The engine ECU and the AT ECU control the engine and the AT on the basis of the commands so that the vehicle axle torque attains the target value.
Thus, the manager exists at an upper level of the control functions for the vehicle and is realized as control logic for managing these control functions, for example, software. Thus, to realize the manager itself, hardware such as inherent special sensors and actuators is not necessary. Accordingly, it is not always necessary that the manager is realized as the manager ECU specialized in its function. It is also realizable, for example, as software in the engine ECU.
It is also possible to realize the manager as software in not only the above engine ECU but also in any ECU included in the ECUs within the network for communication among respective ECUs to integrally control the vehicle.
However, in this case, if a communication failure such as disconnection occurs in the communication network, the communication between the manager and respective ECUs as control elements may stop.
A vehicle integrated control system in which a manager (coordinator) is installed in the engine ECU is proposed as shown in FIG. 12. An engine ECU 50 and an ABS (anti-lock brake system) ECU 60 in the vehicle integrated control system. The ABS ECU 60 is a control function of the ABS as a functional element of the vehicle. The engine ECU 50 and the ABS ECU 60 can communicate with each other through a network with a serial communication line 49 by TTP (time triggered protocol). The serial communication line 49 is a duplex one.
The engine ECU 50 has a driver/receiver IC 51, a protocol IC 52, and a microcomputer 53. The ABS ECU 60 has a driver-receiver IC 61, a protocol IC 62, and a microcomputer 63.
The driver/receiver IC 51 or 61 converts the electric signal received from the serial communication line 49 into digital data that can be dealt with by the protocol ICs 51 and 62 and supplies it to the protocol IC 52 or 62. Moreover, the driver/receiver IC 51 or 61 converts the digital data inputted from the protocol IC 52 or 62 into an electric signal and supplies it to the serial communication line 49.
The protocol IC 52 or 62 processes data inputted from the driver/receiver IC 51 or 61 in accordance with the frame format of the used communication protocol to convert it into data having a format independent of the communication protocol and then supplies it to the microcomputer 53 or 63. Moreover, the protocol IC 52 or 62 effects a process of the frame format such as addition of ID or CRC to the data inputted from the microcomputer 53 or 63 in such a way that the data conforms to the used communication protocol and then supplies it to the driver/receiver IC 51 or 61.
The microcomputer 53 or 63 includes a CPU, a RAM, and a flash memory (not shown). The CPU performs various processes by reading the program (software) stored in the flash memory and executing the program. Moreover, the microcomputer 53 or 63 carries out writing/reading data into/from the RAM in response to the necessity of this processing. In addition, the microcomputer 53 or 63 inputs data from the protocol IC and outputs data for transmission if communication with other ECU is necessary.
In the flash memories in the microcomputers 53 and 63, various programs are stored. More specifically, in the flash memory of the microcomputer 53, a vehicle coordinator 54 and an engine controller 55 are stored as a manager. In the flash memory of the microcomputer 63, an ABS controller 64 is stored. Execution of these programs is started together with the startup of the engine ECU 50 and ABS ECU 60. Moreover, the vehicle coordinator 54 and the engine controller 55 are executed by the same CPU at the same time as different processes.
In this specification, for convenience, the processes by execution of program by the CPU of the microcomputer are described as the process executed by the program itself. For example, “process executed after reading out the engine controller 55 by the CPU of the microcomputer 53” is described as “process executed by engine controller 55”.
The ABS controller 64 executes a process for managing a braking force so as to avoid locked conditions of wheels on the basis of the wheel speed information inputted into the microcomputer 63 from wheel speed sensors (not shown). Moreover, here, the ABS controller 64 receives a command of a braking force from the vehicle coordinator 54 through the serial communication line 49 and executes the process for regulating the braking force on the basis of the command.
The vehicle coordinator 54 performs regulation between the control functions of the engine controller 55 and the ABS controller 64 or the like and commands them.
The engine controller 55 carries out processes such as fuel injection, ignition, and an intake air flow in the engine as to regulation, detection, or the like on the basis of the command from the vehicle coordinator 54.
Moreover, communication among nodes of the vehicle coordinator 54, the ABS controller 64, and other control functions not shown is carried out through the serial communication line 49. The intra-node communication between the vehicle coordinator 54 and the engine controller 55 is performed by inter-process communication.
For example, in such a system, consider that the vehicle coordinator 54 transmits a command of braking operation to the ABS controller 64 to make an emergency stop of traveling of the vehicle. As the cause of the case of emergency stop of traveling of the vehicle, the engine controller 55 may detect an abnormality in an intake air flow to engine and transmits the abnormality to the vehicle coordinator 54 which transmits, on the basis of the reception, the vehicle stop command to the ABS controller 64.
In such a case, if the serial communication line 49 is in the normal condition, the ABS controller 64 can receive this command and operate the ABS on the basis of this command. That is the vehicle can be stopped on emergency.
However, if a failure such as a partial disconnection of the serial communication line 49 in the network occurs, a failure in a device for communication function in the ECU such as the driver/receiver IC 51, the protocol IC 52, the driver/receiver IC 61, and the protocol IC 62, the command of the vehicle coordinator 54 may not reach the ABS controller 64. Namely, there may be the case that the ABS controller 64 cannot effect the barking operation on the basis of the command of the vehicle coordinator 54.
In that case, the vehicle coordinator 54 can stop the fuel injection and ignition of the engine by transmitting commands for stopping the engine to the engine controller 55. However, such an operation effects only gradual deceleration by the engine brake. Thus, the engine does not have the function for making an emergency stop of the traveling vehicle.
The emergency stop function of the traveling vehicle relates to avoiding danger on emergence of the vehicle. As other functions relating to avoiding danger on emergence of the vehicle, there is control for power supply to prevent overcurrent or the like by the alternator for example.